Abstract [en]

Objective: To evaluate the outcome of phototherapeutic keratectomy (PTK) treatment of epithelial basement membrane dystrophy (EBMD) patients and to examine clinical and morphologic signs of recurrent dystrophy. Design: Cross-sectional, clinic-based study. Participants: Fifty-two eyes of 39 patients diagnosed with EBMD who underwent PTK between 2001 and 2008. Methods: Preoperative symptoms, best spectacle-corrected visual acuity (BSCVA), and refraction data were collected. At follow-up, refraction and BSCVA were measured, symptoms were noted, and slit-lamp biomicroscopy and in vivo confocal microscopy (IVCM) were performed. Main Outcome Measures: Best spectacle-corrected visual acuity and signs of recurrent EBMD based on symptoms and morphologic features. An assessment of EBMD severity after PTK additionally was considered. Results: Mean follow-up time was 43 months (range, 7-100 months). After PTK, BSCVA remained unchanged or improved in 49 (98%) of 51 eyes. Twenty-four (46%) of 52 eyes had recurrence of some form, and recurrence was correlated positively with postoperative time (P andlt; 0.001). Symptomatic recurrence occurred in 7 eyes (13%), whereas morphologic recurrence occurred in 21 eyes (40%). Symptoms were coupled with positive IVCM findings in 3 (43%) of 7 cases and with slit-lamp findings in 1 (14%) of 7 cases. Of 17 eyes with morphologic recurrence by IVCM, 9 eyes (53%) were classified as having grade 1 recurrence, 8 eyes (47%) were classified as having grade 2 recurrence, and none were classified as having grade 3 recurrence. Morphologic recurrence was associated with epithelial removal by laser ablation before PTK. Conclusions: Although PTK is an effective method of alleviating the clinical symptoms of EBMD, the dystrophy can recur with time. The relationship between the postoperative development of clinical symptoms and the corneal morphologic features is complex and requires further investigation.

Abstract [en]

Background. Epithelial basement membrane dystrophy (EBMD) is a common disease of the anterior cornea that can lead to problems with vision and/or painful recurrent erosions of the corneal epithelium. Several treatment options have been used, but recurrence of EBMD after treatment is a problem. Excimer laser phototherapeutic keratectomy (PTK) has become an increasingly popular surgical option in recent years due to its accuracy, reproducibility, and good clinical outcomes. When treating EBMD with PTK, the anterior corneal structures including the epithelium, Bowman´s layer (BL), and subbasal nerves are disrupted or removed completely. Little is known about how BL, nerves, and the stroma recover after PTK treatment, or how they could influence recurrence of EBMD symptoms. Additionally, very little is known about the properties and actual thickness of BL in-vivo.

Aims. To improve the understanding and management of EBMD by investigating the clinical diagnosis and treatment of EBMD and its relationship to Bowman´s layer.

Method. An excimer laser was used to treat EBMD patients at the Department of Ophthalmology during the period 2001-2010. IVCM was used to perform pre- and postoperative examinations. In particular, images of anterior corneal structures, cells, and nerves in high-resolution were obtained. Additionally, a group of over 100 healthy volunteers underwent a full ophthalmic examination including IVCM. Other subjects examined in this work included a group of 17 patients who underwent full-thickness transplantation of the cornea.

Results and conclusions. Clinical follow-up revealed that PTK is an effective method of alleviating the clinical symptoms of EBMD, but the dystrophy can recur with time. Recurrence can be divided into clinical and morphologic types, and may depend upon treatment parameters including the type and depth of ablation. IVCM was found to be a useful screening tool pre- and postoperatively, and could prevent patients with symptoms, but no visible signs of EBMD on slit lamp examination, to go undiagnosed and untreated. BL was found to play a role in regenerative wound healing after PTK, and was also found to be important regarding the treatment and recurrence of EBMD. BL may present a physical barrier that protects the subepithelial nerve plexus thereby facilitating sensory recovery, and BL may also serve as a barrier that prevents direct traumatic contact with the corneal stroma, avoiding a stromal wound healing response. To aid in accurate assessment of BL in patients, an in vivo method for determining BL thickness was developed. This method could be an important tool to aid in clinical assessment and planned treatments of the anterior cornea. Using this tool, a large inter-individual variability in BL thickness and a strong negative correlation of BL thickness with age were found in a healthy population. Using IVCM, it was also found that subbasal nerves are pathologically reduced in EBMD compared to a healthy population, and that this nerve deficit does not improve in the long term after PTK treatment.